Odd Ophiuchus

Half of the constellations of the zodiac line up across the south as night falls this evening like charms on a celestial bracelet. They stretch from Cancer, the crab, which is quite low in the west, to Leo, Virgo, Libra, Scorpius, and finally Sagittarius low in the southeast.

Ancient skywatchers assigned special significance to these constellations because they’re on the ecliptic — the Sun’s path across the sky — so the Sun passes through them each year.

Another constellation also lies along this path, but it’s not a member of the zodiac. Ophiuchus is above Sagittarius and Scorpius as night falls. Its brightest stars form a faint, wide-spread pattern that slightly resembles an old coffee pot.

Ophiuchus didn’t make the list of zodiacal constellations because the Sun doesn’t cross the coffee pot — the classical depiction of the constellation. Instead, it just nips across the southern edge of the modern version of the constellation, which consists of not just the classical star pattern, but the area around that pattern as well.

In fact, all of the modern constellations have specified borders. That turns the sky into a giant patchwork quilt — 88 patches in all. They’re of many different sizes and shapes. Some are simple rectangles, but most have odd notches and appendages to accommodate the classical star patterns. The borders of Ophiuchus comprise 38 individual segments — an oddly shaped patch that just intersects the ecliptic.

Script by Damond Benningfield, Copyright 2013

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